Astronomy Part 3

How many planets in the solar system are there?

• 4
• 8
• 9
• 13

What process heated the early solar nebula as it slowly condensed toward a central protosun?

• thermonuclear fusion in the protosun, followed by radiative heating of the material of the nebula
• release of heat from the kinetic energy in collisions of particles as they fall toward the center of the nebula
• release of heat as molecules such as CO₂ and NH₃ form from atoms and ices condense from gases such as H₂O

How old is the Earth?

• about 6000 years old
• about 4.6 million years old
• about 4.6 billion years old
• about 13.7 billion years old

What is the smallest planet?

• Venus
• Jupiter
• Uranus
• Mercury

The most abundant elements in the universe are hydrogen and helium, but there are also small but significant amounts of heavier elements in stars and planets and in our own bodies. Where did these heavy elements originate? 

• in collisions between element nuclei in space, which produced heavier elements by nuclear fusion
• in nuclear fusion during the Big Bang 
• in nuclear fusion deep in the interiors of stars

How are most planets orbiting other stars detected?

• the planets are observed directly
• by the alternating Doppler shifts of the stars
• by the change in color of the star as the planet passes in front of it
• by the motions of moons around these planets

The planets that have been discovered outside the solar system are typically most similar in mass to which of the following?

• the Sun
• the Earth
• Pluto
• Jupiter

Rock and metal debris smaller than asteroids is called:

• planets
• planetesimals
• meteoroids
• comets

Planetesimals collide and stick together to form protoplanets because

• of their mutually attractive gravitation.
• they are weakly charged and can attract each other.
• chemical bonds hold them together if they happen to collide.
• Both b and c

Which aspect of the early solar nebula controlled the early evolution and place of formation of the terrestrial and the Jovian planets?

• The rotation of the nebula
• Distribution of hydrogen in the nebula
• Distribution of silicates in the nebula
• Temperature distribution within the nebula